80 ILLINOIS BIOLOGICAL MONOGRAPHS (398 



3 setiferous; thoracic legs spreading laterad, normal in form; larvapods 

 setiferous, normal in form, except the anal pair, which is reduced in size, 

 only one-half as large as the other pairs; tenth abdominal tergum with- 

 out the paired caudal protuberances; head circular, smaller than thorax 

 in width and height, front flattened; antennae apparently with four seg- 

 ments, flattened, all segments fused together; ventral glands very large; 

 setae sparse, very long; spiracles not winged; suranal and subanal lobes 

 multisetiferous; glandubae subsessile; free leaf-feeders. 



Konow in 1905 listed three species of Micronematus: abbreviatus, 

 calijornicus, and monogyniae. The second species properly belongs to 

 Diphadnus. Of the two remaining species, M. abbreviatus was recognized 

 in the larval stages a long time ago by Snellen von Vollenhoven (1868). 

 This genus is European and is represented in North America by a single 

 species, Micronematus gregarius Marlatt. That this species does not 

 belong to Pachynematus can be readily seen from the structure and 

 biological characters of the larvae as was suggested by Dyar (1897) 

 in his original description of the immature stages. Three facts distinguish 

 this species from all other known species of Pachynematus: (1) the larva 

 has five annulets instead of six; (2) the anal larvapods are very much reduced 

 in size; and (3) the larva feeds on willow instead of grasses. On the other 

 hand M. gregarius has certain characters in common with M. abbreviatus 

 as recorded by Vollenhoven. Since this species can not be referred to 

 Pachynematus or to any other known American genus, and since it has 

 characters which are peculiar to Micronematus, and since the adult 

 characters, according to Ashmead (1898), would place it in this genus, 

 this species is here considered as belonging to Micronematus. If future 

 study should prove this position untenable, a new genus should be erected, 



Micronematus gregarious Marlatt. — Length, 12 mm.; body shiny, 

 yellowish white; alimentary canal showing thru as green tube; head pale 

 testaceous with a broad blackish band across the front between ocellarae 

 and a narrow band dorsad of each ocellara to and along vertical furrow; 

 mouth-parts, cervical sclerites, and legs except coriae brownish; abdominal 

 segments 1-8 with postspiracular and subspiracular areas swollen, mound- 

 like, and tinted fuscous; abdominal segments 2-7 with colored postspiracu- 

 lar areas larger than subspiracular areas; those on segments 1 and 8 much 

 smaller; thoracic segments with two colored patches on latus, one larger 

 and more ventral than the other; larvapods with about two setae on the 

 cephalo-lateral aspect; ventral glands nearly three times as large as larva- 

 pods; setae slender, at least twice as long as spiracles; spiracles not winged; 

 subspiracular area with two setae and single glanduba, surpedal area 

 with 3-4 setae and single glanduba; larvae gregarious; on Salix; Y. 



